Dental impression composition



Patented Oct. 13, 1942 OFFICE DENTAL IMPRESSION COMPOSITION Stanley E. Noyes, Los Angeles, Calif.

No Drawing. Application November 7, 1941 Serial No. 418,167

6 Claims.

This invention relates to a dental composition, and more specifically it relates to a composition of matter suitable for use by dentists or dental technicians in making impressions of the teeth and gums and is a continuation in part of my application, Serial Number 195541, filed March 12, 1938.

For many dental purposes, such as the making of full or partial dentures, bridges, inlays. etc., it is necessary for the dentist to be able to reproduce accurately portions of the mouth of the subject. Such reproductions often involve the duplication of undercuts of more or less severity, as for. instance in cases where a tooth or teeth have been extracted and the adjacent teeth have crowded together.

Impression materials such as plaster of Paris or the various shellac and wax compositions, which have been used for. many years, have little or no elasticity, making reproduction of undercuts very diflicult, the procedure involving either breaking the impression in sections, as is the practice with shellac and wax compounds. Such methods are obviously time consuming and involve danger of inaccuracy and discomfort to the patient.

By the use of an impression material which may be introduced in the mouth in a fluid or plastic condition and cooled to an elastic state, it is possible to take an impression which accurately reproduces all details of the portion of the mouth under examination, and which due to its elasticity, can be removed from any undercuts' present without losing the accuracy of the impression.

Due to the narrow range of temperature which the human mouth can stand, rather strict limitations are placed on the types of elastic materials which can be used. These materials must obviously be either fluid or plastic when they are heated to place in the mouth, and must change by cooling to elastic gels which will permit removal from the undercuts without permanent distortion. They must-also be sufficiently tough and rigid so that they may be used as molds for models of plaster or other compounds to be poured into them.

It is possible by the use of a hydro-colloid to obtain a compound which is a viscous fluid when slightly warmed, and which cools at mouth temperature or by the use of ice water to a gel which is sufllclently elastic to reproduce undercuts properly, and which-can with care be handled and used as a mold to receive plaster; Several such hydro-colloid compositions have been proposed, usually using agar-agar as a base. They have all been relatively fragile and easily injured when handled, and have contained so much water that great care was necessary to prevent evaporation from the impression with accompanying change of shape or size. Some of them have contained added ingredients, such as copal, pontianak, balata, rubber latex and polymerized rubber to toughen them, and some have contained added materials, such as potassium sulphate to facilitate the set of plaster against the surface of the impression.

My invention provides an impression material having elastic properties as above mentioned, but in addition having greatly increased strength an toughness to facilitate handling of the impression, having less tendency to change in shape or size by evaporation of water from the impression, and having a surface against which plaster of Paris sets satisfactorily. Also, my material can be carried to the mouth at much lower temperatures, consequently removes the hazard of burning, andupon applying cold water congeals faster.

Agar-agar, when dissolved in water, forms gel at very low concentrations, a 1% solution setting to a fairly stiff jelly. Ordinary dental 1111-,

pression materials using an agar-agar base, employ proportions of one part agar-agar to from 10 to 15 parts of water, giving a stiff gel, but one from which water evaporates readily with resulting change .in shape or size. My invention provides for a composition with a preferred propor tion of 1 part agar-agar to from 8 to 10 parts of water, which greatly reduces the tendency for the water to evaporate rapidly. While this would be difllcult to mix smoothly under ordinary conditions, mixing is readily accomplished by,heating under" low steam pressure of from 7 to 10 pounds (200-218" F.) preferably with agitation.

Ordinary dental impression materials of the hydro-colloid type are fragile, thin sections breaking readily when sharply bent, and requiring very great care in handling. Other materials, upon heating need mixing or kneading to make them a smooth cream consistency, whereas my material upon heating needs neither mixing nor kneading and is a smooth cream-like consistency. My invention provides for the use of esters of polyhydric alcohols and borlc acid as plasticizing and toughening agents, by which use the material is so toughened that thin sections may be bent double without breaking Such toughened hydro-colloid gels alone will not permit plaster to set satisfactorily against their surfaces. the surface of the plaster being soft and spongy. It is possible to dip or otherwise coat the gel surfacm with acids or solutions of salts, suchas potassium sulphate, alum, or other sulphates, chlorides or chlorates, to aid the set of plaster. In fact, this is often done with ordinary impression materials of the hydro-colloid type, but this is a troublesome extra operation, and is liable to render the impression less accurate. My invention provides for the incorporation of a suitable hardening agent in the composition, suchagent being preferably manganese sulphate, which confers the property of allowing plaster to set against the surface of the impression without adding deleterious properties of taste, discoloration, reducing the viscosity of the fluid when the gel is heated, etc. Hardening agents, such as sodium, potassium chloride or sulphate introduce such deleterious properties and are much inferior to manganese sulphate for this purpose.

As an example of a composition which I have found to be highly satisfactory for making dental impressions is as follows:

. Grams Agar-agar 1,400 Water 12,000 Manganese sulphate (anhydrous) 80 Red iron oxide 15 Titanium oxide 43 Salicylic acid 4 Sodium perborate 27 Sodium silicate 140 Lead oxide 325 Oil of Cassia 3 The foregoing materials, in the proportions shown, are compounded as follows: the agaragar, water, 80 grams of the manganese sulphate and all of the iron oxide, titanium oxide and salicylic acid are placed in an autoclave and heated with agitation at approximately 200 F. to 218 F. for approximately one hour. Too long heating or too high a temperature tends to lower the viscosity of the mixture and renders it too fluid for use. The time and temperature of heating also require adjustment to the grade of agar-agar used. The iron oxide and the titanium oxide are introduced to color the mixture, and may be omitted if desired and other materials substituted. The salicyclic acid is employed to sterilize the material and prevent growth of molds or bacteria if any of it is allowed to stand exposed to air and may also be omitted if desired and other materials of relative value be substituted.

After the heating period is complete the combination of sodium perborate and sodium silicate is added and after being thoroughly mixed a combination of boric acid and sodium perborate is added. After this material has been thoroughly mixed the lead oxide, which combines with the foregoing ingredients, is added and it is quite evident that lead perborate is formed to some extent and creates a toughening agent and drier which in turn will allow dental stones or plaster of Paris to set. Oil of Cassia is employed merely as a flav'or and perfume and similar flavors may be substituted.

It has been found that most of the sulphates or chlorides will react much like the above but will not give the same result as these materials do not allow the dental stones or plaster of Paris to set as firmly or within the same period of time.

I have also found that this combination, allowing the mixture showing poly-glycerol alcohols such as glycerine, etc., will also combine and produce approximately the same results. By omitting the iron and iron oxide and substituting a material that will not ironize and adding to this mixture wax, oils, resins or artificial resins, the material can be plated with copper, nickel, chromium, etc., which is an invention-within itself, as no material at the present time compounded or manufactured will accept a copper plating and withstand the acid bath of the copper plate solution. To control and to decrease the time of the plaster or dental stone set is regulated by the amount of manganese sulphate, or other sulphates or chlorides, used in conjunction with the chemicals manufactured.

In the preceding disclosure various esters of boric acid, poly-glycerol, mono, di and tri ethylene glycol, etc., can be used as plasticizers and toughening agents, the proportions being suitably varied for the particular compound to be used to secure strength and the stiffness desired and to allow the dental stones and plasters to set. This compound can be modified to obtain diiferent results and character by varying the amounts of the foregoing chemicals, manganese sulphates or other sulphates, potassium chlorates or perchlorates, chlorides or similar substances, etc., the amount of glycerine or poly-gl cerol, mono, di and tri ethylene glycerol, etc.

By heating together sodium perborate, etc., and boric acid, glycerine, etc. to bring to a honeylike consistency or otherwise under heating pressure will give the same result as that obtained by using sodium silicate.

It has been found by tests that lithage has a very definite reaction with agar-agar in combination with sulphates, chlorides, chlorates, and so forth and this action can be varied or governed by the amount of the above chemicals employed and may also be changed or governed by adding the material at various stages of the cooking process. It has also been found that by the addition of silicates and similar materials the body of the material can be substantially increased and becomes of putty-like consistency.

I claim:

1. An impression material comprising a reversible gel-forming hydro-colloid base, an alkali metal perborate and manganese sulphate.

2. An impression material comprising a reversible gel-forming hydro-colloid base, sodium perborate and manganese sulphate.

3. An impression material comprising a reversible gel-forming hydro-colloid base, potassium perborate and manganese sulphate.

4. An impression material comprising agar- .agar, an alkali metal perborate and manganese sulphate.

5. An impression material comprising agaragar, sodium perborate and manganese sulphate.

6. An impression material comprising approximately 1400 grams of agar-agar, 12,000 grams of water, grams of manganese sulphate and 27 grams ofsodium perborate.

STANLEY E. NOYES. 

